<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        body {
            background-color: #bbb;
        }

        #canvas {
            background-color: #fff;
        }
    </style>
</head>

<body>
    <canvas id="canvas" width="400" height="400"></canvas>
</body>
<script src="./ball.js"></script>
<script src="./utils.js"></script>
<script>
    window.onload = () => {
        var canvas = document.getElementById("canvas");
        var context = canvas.getContext("2d");
        var ball = new Ball();

        var angle = 0, angleX = 0, angleY = 0;
        var range = 50;
        var centerX = canvas.width / 2, centerY = canvas.height / 2;
        var speed = 0.05, xspeed = 1, yspeed = 0.05;
        var xpos = 0, ypos = centerY;
        var radiusX = 150, radiusY = 100;

        (function drawFrame() {
            window.requestAnimationFrame(drawFrame, canvas);
            // 每一帧开始的时候清除上一次的绘画
            context.clearRect(0, 0, canvas.width, canvas.height);

            ball.x = centerX + Math.sin(angle) * radiusX;
            ball.y = centerY + Math.cos(angle) * radiusY;
            angle += speed;
            ball.draw(context);
        }());
    };
</script>

</html>